London - Workers in Turkey who stitched pleas for help into clothing sold by retailer Zara are "just the tip of the iceberg" and highlight the need for mechanisms to address concerns about labour conditions, a top human rights expert said on Wednesday.

Shoppers in Istanbul discovered notes in clothing saying workers had not been paid at the Bravo Tekstil factory in Turkey, according to widespread media reports this month.

Zara's parent company Inditex has said it will launch a fund to help compensate the unpaid workers, but such funds can fall short or even backfire, said John Morrison, chief executive of Britain's Institute for Human Rights and Business.

"Workers are often very scared to (publicly complain), so you can imagine how bad the situation is," Morrison said on the sidelines of the Thomson Reuters Foundation's annual two-day Trust Conference that focuses on forced labour and other issues.

"I think it's the tip of the iceberg," Morrison said.

Bravo Tekstil, which supplied garments to Zara and other brands, shut down in 2016 owing wages and severance payments to 140 workers, according to reports.

Inditex, a Spanish retail giant whose brands include Zara, did not immediately respond to a request for comment.

Since the campaign began, thousands of people have been posting support for the workers on social media using the hashtag #BravoIscileriIcinAdalet, which translates as "Justice for Bravo workers".

Morrison said such a move by desperate workers shows a need for effective mechanisms that allow them to air grievances and complaints and seek justice without fear of retribution.

"When factories have a grievance mechanism that the workers actually trust and they think is going to be effective, they don't do things like that," he said.

Zara has said its so-called hardship fund would help the affected workers who, according to reports, are seeking 2,739,281 Turkish Lira ($705,000).

Reparation funds are valuable but can be tricky to implement, Morrison told the Thomson Reuters Foundation.

"They're not tackling the underlying issue," he said. "They're important for individual victims, but if there's a system that's wrong, then you're going to have more and more victims coming."

Also, he said, corrupt labour recruiters who connect workers with jobs can get their hands on that money as well.

"You've got to make sure when you do that, that you're not just putting more money into a corrupt system," he said.